C for Java programmers Top tips to help the Java programmer code in C Very common errors noted in preliminary exercises. 1) TRUE/FALSE/0/1? There is no boolean type in C. 0 : FALSE 1, or anything other than 0 : TRUE e.g. -1, 25, 1, 1389 all evaluate to TRUE For further explanation please look here. 2) == and = == Boolean evaluation = Variable assignment operator Classic cause of problems in C, which I think is caught at compile time in Java. NOT NECESSARILY IN C e.g. int a; a=0; // FALSE if (a=1){ . . some stuff . } This will result in 'some stuff' being executed regardless of the value of a. WHY? Because (a=1) assigns the value 1 to a and the overall expression (a=1) returns 1 in C. This is permissible in C, although the compiler should warn you. A good habit to get into is always placing the constant on the left of boolean expressions. Do you know why? 3) No function overloading in C Two functions cannot have the same name in C. 4) Variables must be declared at the top of a basic block. e.g. The following is OK { int a; char b; . . printf("Hello world\n"); . . } However, this is not OK { int a; . . . printf("Hello world\n"); . . char b; . . . } 5. If you MALLOC memory then you must free it (no automated garbage collection in C) (Unlikely you will have to worry about this in practical#2) Some useful links Learning C from Java Differences between C and Java Essentials of C Summary of basic C language features Simple C examples Pointers in C A tutorial on pointers and arrays in C A silly pointer example Programming in C UNIX System Calls and Subroutines (Advanced) Some C Text books in the library The C programming language / Brian W. Kernighan, Dennis M. Richie Book on C: programming in C / Al Kelley and Ira Pohl ANSI C: problem solving and programming / Kenneth A. Barclay Could not open counter file
